Dynesys System As An Alternative to Fusion Surgery for Lumbar SpondylolisthesisBack and leg pain in the older adult population is often caused by spinal stenosis (narrowing of the spinal canal). And a common cause of the stenosis is degenerative lumbar spondylolisthesis (one vertebra slips forward over another). In this study, the use of a Dynesys system to stabilize the spine is investigated.
The Dynesys is a long screw that goes through the pedicle into the vertebral body to hold it in place. The pedicle is the segment between the transverse process and the vertebral body. There are two transverse processes in each vertebra. They project out from either side where the lamina joins the pedicle. These bones attach to the back of the spinal column, forming a bony ring that encloses the spinal canal. They serve for the attachment of muscles and ligaments.
Using the Dynesys system eliminates the need for bone graft to complete the fusion. The patient is spared any suffering from the removal of bone at a donor site. But this is a fairly new procedure and long-term results aren't available yet. This study presents the results after four years. A previous study by the same authors reported the results after the first two years.
The patients included in the study had a single level degenerative spondylolisthesis. They all had leg pain with or without back or buttock pain. Open surgery was performed to take pressure off the spinal nerves. The procedure is called a decompressive laminotomy. The lamina isn't removed entirely. Just a portion is taken out to remove pressure from the spinal canal.
The Dynesys pedicle screws were placed without trying to change the position of the vertebrae. Everyone wore a back brace for three months. Then they gradually resumed their normal activities.
Data was collected for two years and reviewed. The results were published in 2006. The same patients were then followed for another two years. The same measures were used to assess clinical outcomes. These included pain (location and intensity), walking distance, lumbar spine mobility, and activity level. The researchers also looked at the patient's occupation, pain medications used, and complications caused by the surgery. Any other spine surgeries done were also recorded.
Only 19 patients of the original group (26 total) could be studied. Several patients had died or developed other more serious medical conditions. One patient had moved out of the country. Several others had additional lumbar surgery after the first procedure to implant the Dynesys system.
Overall, the group reported good results. Partial or complete pain relief was possible for 84 per cent of the group. All but one patient reported improvement of some kind. Walking distance improved quite a bit. Two-thirds of the group were able to stop taking pain medication.
At the two-year check-up, X-rays showed four patients who had a loose or broken screw but the spinal segment was still stable. At the end of four years, this remained unchanged. But there was degeneration observed at the next spinal level in almost half the patients.
This was the first report of long-term results with the Dynesys stabilization system. The good news is that it is possible to decompress and stabilize degenerative lumbar spondylolisthesis without the added step of the bone harvesting and grafting. The segment remains stable over a four-year period of time.
The system does not prevent degeneration at the next spinal level. Rate of change at the adjacent vertebral level is about the same as reported after spinal fusion. But there is some evidence from other studies that the degeneration isn't caused by the dynamic stabilization process. It could very well just be a natural progression of aging.
Further studies are needed with larger groups of patients over a longer period of time. For now, the authors conclude that dynamic stabilization is provided by the Dynesys system. It can be used instead of the more invasive bone grafting process.
Stefan Schaeren, MD, et al. Minimum Four-Year Follow-Up of Spinal Stenosis with Degenerative Spondylolisthesis Treated With Decompression and Dynamic Stabilization. In Spine. August 15, 2008. Vol. 33. No. 18. Pp. E636-E642.
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